This document discusses different types of relationship modeling in entity-relationship diagrams including: 1) Reinterpreted relationship types which are used to further model other elements rather than just connections and can become multi-valued or specialized. 2) Different types of generalization/specialization including non-disjoint and partial relationships as well as disjoint and total relationships. 3) Modeling conventions for key attributes, non-key attributes, and how keys and foreign keys are modeled based on relationship cardinalities.

1. AdvancedConceptual Data Modelling(Entity-Relationship Model)

2. Reinterpreted Relationship TypesWhen to use a Reinterpreted Relationship Type? Simple Case: If a relationship type is not used for connections to other model elements, he stays uninterpreted. If a relationship type is used for further modelling, he will either be reinterpreted or will become a multiple relationship type (n>2).

3. Generalization/Specialization (N,P)Therearevariousformsofstudents. The relationship is non-disjunct (N) because a PhDstudent in thesubjectinformationsystemscan also be a bachelorstudent in philosophy.The relationship is partial (P) becausethereare also othertypesofStudents such asmasterstudents, executivemasterstudents, etc.

4. Generalization/Specialization (N,T)An animalcanbe male orfemaleorboth (e.g. snail) (not disjunct (N)).Therearenootherformsofsexuality (T). Tosomeextend

5. Generalization/Specialization (D,P)A personcaneitherbe a man or a woman (D). Thereare also othertypesliketransexuals (P)whoareneitherwomannor man.Tosomeextend

6. Generalisization/Specialization (D,T)A personcaneitherbe a male or a femaleperson (D). Therearenoothertypes (T).Tosomeextend

7. Modelling Conventions (Summary)Key Attribute consistofName oftheEntity Type„ID“ or „Nr“andhavetobeunderlinedNon-Key Attributes will not beunderlinedKey Attributes will bemodelledtoEntityTypesexclusively.Howandwhatkeys a relationship type receivesis due toitscardinalities. They will notbemodelled. The same is valid forForeignKeys.Additional Non-Key Attributes of a Relationship Type will bemodelled. Itisonlypossiblewith(x,n)-(x,n) relations (x=0 v x=1).

8. AdvancedConceptual Data Modelling(Entity-Relationship Model)